1. Field of the Invention
The present invention relates to an automatic film feeding apparatus for a camera and, more particularly, to an automatic film feeding apparatus for a camera using a film cartridge in which a nonexposed film is automatically supplied from the film cartridge by rotation of a supply spool in the film cartridge in one direction, and an exposed film is automatically rewound by rotation of the supply spool in the other direction.
The present invention also relates to an automatic film feeding apparatus for a camera in which photographic preparation is performed by automatically feeding a film from a film cartridge loaded in a camera body.
2. Description of the Related Art
In a conventional film cartridge, a film is automatically rewound by rotating a cartridge shaft in a rewinding direction, and the film is supplied as follows. That is, the film is loaded in the camera such that one end of the film is manually fed to be close to a take-up spool, and the film is taken up by the take-up spool. In this state, the film is wound on the spool. Therefore, when the film cartridge is only loaded in the camera, the film cannot be automatically supplied, and a cumbersome operation must be performed.
In recent years, in order to decrease the number of manual operations of a photographer and to prevent erroneous operations, countermeasures have been proposed in which a film is wound on a spool by a driving source such as a motor after a film is loaded in a camera body, thereby performing photographic preparation.
For example, a film cartridge of a new type in which a film is automatically supplied by the rotation of a supply spool of the film cartridge in one direction has been proposed (Published Unexamined Japanese Patent Application No. 2-67534). Since the newly proposed film cartridge can automatically supply/rewind the film by the same driving member, a photographer is required only to load the newly proposed film cartridge in the camera, and he or she need not pull one end of the film. A cumbersome operation in film loading operation can be considerably reduced.
However, in the newly proposed film cartridge, when a user erroneously opens the rear cover of the camera during a film supply operation, the film is supplied out of the rear cover, and a nonexposed film portion is unnecessarily exposed. That is, since a conventional film cartridge itself does not have a film supply function, even when the rear cover is opened, the film is not further supplied from the cartridge. However, since the newly proposed film cartridge itself has a film supply function, the nonexposed film may be unconditionally supplied.
In addition, a film feeding apparatus capable of easily being operated and having a conventionally used film cartridge is described in Published Unexamined Japanese Patent Application No. 2-151844.
In each of the techniques described in the Published Unexamined Japanese Patent Application Nos. 2-67534 and 2-151844, a film stored in the film cartridge is automatically supplied to reach a film take-up spool mounted in the camera body, and the film is taken up by the film take-up spool.
In order to automatically wind a film on the take-up spool, two conventional techniques are used. That is, first, as one technique, a film is wound on the take-up spool using a frictional force between the film and the take-up spool. Second, as the other technique, lock pawls formed on an outer peripheral surface of the take-up spool are engaged with perforations formed in the film.
A normal photographic film has an elastic coefficient changed in accordance with the application conditions such as an atmospheric temperature, of a camera. Therefore, when the film is wound on the take-up spool using the frictional force between the film and the take-up spool, if the elastic coefficient of the film is large due to a low atmospheric temperature, the film is not properly curved along the take-up spool, and the film cannot be easily wound on the take-up spool. In addition, when the method of winding the film by engaging the lock pawls of the take-up spool with the perforations of the film is used, since shearing strength of the film is decreased in accordance with a decrease in temperature of the film, the perforations and other parts of the film cannot withstand the engaging force of the lock pawls and are damaged, and the film cannot be wound on the take-up spool.
In a normal state, when a winding operation of a film is impossible, the position of a film leader is slightly changed when the film is loaded so as to change the condition in which the winding operation is impossible. At this time, the film can be often wound. Therefore, in a conventional automatic film loading apparatus, when a film cannot be wound, a photographer changes the position of the film leader and loads the film in the camera again.
However, when the film is to be reloaded in the camera body, a photographer determines whether the position of the film leader is changed or not. Beginners rarely execute this determination, and repeat operations such as reloading and impossible winding many times or give up loading the film in the camera body.